Question

What is opsonization in the context of the immune response?

a) Aggregation or clumping of cells or particles.
b) Assembly of large antigen-antibody complexes that precipitate from solution.
c) Blocking of structures on microbes and toxins.
d) Increased phagocytic uptake of cells or molecules.
e) Complement activation initiated by antibody attachment.

Answer 1

Option (e), Opsonization in the context of the immune response is the enhancement of phagocytosis by coating pathogens with molecules, particularly IgG antibodies and complement factors, that facilitate their uptake by phagocytic cells.

Step-by-step explanation:

Opsonization is a critical mechanism within the immune response that involves the coating of pathogens with specific molecules to enhance their recognition and subsequent phagocytosis by immune cells such as macrophages, dendritic cells, and neutrophils. These molecules may include complement factors, C-reactive protein, serum amyloid A, and especially IgG antibodies.

The IgG antibodies serve as excellent opsonins, attaching their Fab sites to epitopes on the pathogen's surface. Phagocytic cells have receptors that recognize and bind to the Fc portion of these IgG molecules, which assists in the engulfing of pathogens during phagocytosis. Additionally, the process of complement fixation involves IgM and IgG in the serum binding to antigens, providing sites for complement proteins to attach, thus promoting rapid clearance of pathogens through enhanced opsonization.